As an example, you could change the eye position to, for example, (0.0, 0.0, 10.0) and pointing to (0.0, 0.0, -1.0) as follows:
gluLookAt (0.0, 0.0, 10.0, 0.0, 0.0, -1.0, 0.0, 1.0, 0.0);
instead of drawing everything with z less than it is supposed to be